KIEV, Ukraine — In the midst of Ukraine’s revolution, the pop singer Svyatoslav I. Vakarchuk jumped onto a stage before almost a quarter of a million protesters. With steam billowing from his mouth in the frigid air, he clenched a microphone wrapped in Ukraine’s blue and yellow flag and sang to his country: “My darling! Rise up my dear! Wake up!”

.... His political clout is indisputable. Three of his songs, songs “Almost Spring” and “Without a Fight,” as well as “Rise Up, My Dear,” became the protest anthems for two successful street uprisings in Ukraine, in 2004 and 2014. But each time, he and millions of Ukrainians became disillusioned as the leaders they helped put into power turned out to be as cynically rapacious as their predecessors.